1. Field of the Invention
This invention relates to an additive which imparts haze-free rust inhibition to diesel lubricating oils, and to a diesel lubricating oil composition which contains such an additive. More specifically, this invention relates to a diesel lubricating oil additive which comprises the reaction product of a maleimide and an amino-triazole, and to a diesel lubricating oil composition in which the additive of the present invention is dissolved.
2. Description of Related Information
As is well known to those skilled in the art, lubricating oils must be characterized by resistance to oxidation, and by rust and corrosion inhibition. It is also desirable from aesthetic perspective to have a haze-free product. The oils used as lubricants in the crankcases of large diesel engines, such as marine and railway diesel engines, are subject to uniquely harsh operating conditions and thus special attention must be directed to the severe problems which are encountered. These oils are therefore typically formulated to contain anti-wear additives, oxidation inhibitors, demulsifying agents, rust-inhibitors, etc.
Lubricants used in the crankcases of marine diesel engines are burdened by a severe rust protection requirement. The rust forms as the result of water coming into contact with ferrous metal engine parts. There are two water sources which are responsible: the first is water produced by the combustion of the diesel fuel; the second is seawater. Of the two, seawater is considerably more abundant and corrosive.
This is an old problem, and diesel lubricating oils have been formulated with additives to inhibit the formation of rust. However, the treatment of one problem, i.e., rust formation, has introduced another problem. The addition of rust inhibitors to lubricating oil compositions has been found to cause the formation of haze in the lubricating oil. The formation of haze is undesirable since it masks or interferes with the determination of the presence of undesirable components, including decomposition products, water, and solid particles in the lubricant.
In addition, consumers have come to equate product clarity or aesthetics with product superiority. In this context, hazy products would dramatically curtail product acceptance by consumers.
The advent of new, more fuel efficient railway diesel engines has put a greater demand on the oxidation resistance of railway diesel lubricants. Oxidized lubricants lead to increased corrosive attack of engine metal surfaces; consequently, lubricants employed in newer railway diesel engines must be changed more frequently to prevent such corrosive attack.
Thus, there is a need for an additive which will impart rust inhibition to diesel lubricating oil compositions, but which does not cause haze to form.
It is an object of this invention to provide a diesel lubricant additive which will inhibit the formation of rust in a lubricating oil, but which will not cause undesirable haze to form. It is another object to provide a novel lubricant composition, suitable for use in large marine and railway diesel engines, characterized by its rust and haze resistance. It is still a another object of this invention to provide a process for producing such a lubricating oil additive and a method for imparting rust resistance to a lubricating oil without causing haze to form. Other objects will be apparent to those skilled in the art.